Decreasing incidence of Acinetobacter baumannii pneumonia and trends in antibiotic consumption: A single-center retrospective observational study

Objective: To describe the epidemiology of Acinetobacter baumannnii (AB) pneumonia at our center, including the antibiotic exposure patterns of individual AB pneumonia cases and to investigate whether hospital-wide antibiotic consumption trends were associated with trends in AB pneumonia incidence. Design: Single-center retrospective study with case-control and ecological components. Setting: US private tertiary-care hospital. Participants and methods: All hospitalized patients with AB infection from 2008 to 2019 were identified through laboratory records; for those with AB pneumonia, medical records were queried for detailed characteristics and antibiotic exposures in the 30 days preceding pneumonia diagnosis. Hospital-wide antibiotic consumption data from 2015 through 2019 were obtained through pharmacy records. Results: Incidence of both pneumonia and nonrespiratory AB infections decreased from 2008 to 2019. Among the 175 patients with AB pneumonia, the most frequent antibiotic exposure was vancomycin (101 patients). During the 2015-2019 period when hospital-wide antibiotic consumption data were available, carbapenem consumption increased, and trends negatively correlated with those of AB pneumonia (r =-0.48; P =.031) and AB infection at any site (r =-0.63; P =.003). Conversely, the decline in AB infection at any site correlated positively with concurrent declines in vancomycin (r = 0.55; P =.012) and quinolone consumption (r = 0.51; P =.022). Conclusions: We observed decreasing incidence of AB infection despite concurrently increasing carbapenem consumption, possibly associated with declining vancomycin and quinolone consumption. Future research should evaluate a potential role for glycopeptide and quinolone exposure in the pathogenesis of AB infection.